1. Field of Invention
The present invention relates to heat exchangers, specifically to a disk type heat exchanger unit with plurality of tubes and disk units for transporting heat exchange media within.
2. Discussion of the Related Art
Heat exchangers are used in various applications where heat from one media is desired to be transported to another media. Typical heat exchangers are made of tubes with plurality of fin attachments on surface of tubes. Heat exchange media is transported through tubes, carrying heat within the media. The heat transported through tubes by means of heat exchange media is then transported within a tube and fin structure, as the heat exchange media flow through tubes. The tube and fin structure is surrounded by another heat exchange media, absorbing away heat from the tube and fin structure. The efficiency of a heat exchanger is dictated by the ratio of volumetric capacity of tubes to the overall surface area of tubes and fins. Typical application of this type of high performance heat exchangers are condensers and evaporators for use in commercial and residential air conditioner units. Variants of this type of heat exchangers are commonly utilized in commercial and automotive applications as oil coolers, evaporators, condensers, heater cores, and radiators.
Efforts to enhance performance of heat exchangers is generally achieved by creating complex fin structures that have myriad bends and folds to create as much surface area within a given confine. Fins effectively increase surface area of tubes. In another effort to improve the performance, fins in addition to bends and folds may have plurality of louver features created on surface of fins. High performance heat exchangers are generally utilized where space is restricted, thus achieving higher performance with heat exchangers of smaller footprint. Enhancement efforts by means of utilizing complex fin structures may improve performance of heat exchangers, but potential additional manufacturing processes may adversely affect a total manufacturing cost of heat exchangers.
In another embodiment of this effort, instead of round tubes, flat tubes are made with plurality of small diameter holes. Generally of aluminum extrusion, intricate tubes are made with plurality of small diameter holes. To further improve performance of heat exchangers, thickness of a material used to create fins and tubes may be made thinner. By making the thickness of a material thinner, performance of a heat exchangers may be improved by shortening a distance that heat has to travel within walls of tubes and fins structures, improving heat conduction efficiency. Thinning a material has the adverse effect of weakening a structure, however. Also, in an application such as automobiles where potential for debris hitting a heat exchanger surface is high, having a weak structure is not favorable, as a heat exchanger may be easily damaged, or worse having a puncture within tubes, causing heat exchange media within to leak out, rendering the heat exchanger useless. A manufacturing process of assembling together various heat exchanger components may be complicated as well, when components utilized are manufactured of thin walled tubes and fins. Complication of manufacturing method typically has an adverse effect on the manufacturing cost, generally raising cost of individual components. Fragile components may also complicate handling of components during an assembly stage, as well as requiring stricter tolerance components as well as assembly machines capable of meeting strict tolerances, all of these factors typically resulting in higher component costs and assembly costs.
A variation on a tube-based heat exchanger involves stacking flat, ribbed plates. When said flat, ribbed plates are stacked upon each other, said plates create chambers for transferring heat exchanging media. In essence, this type of heat exchanger performs substantially the same function as tube-and-fin type heat exchangers, but is fabricated differently. This type of heat exchanger is commonly implemented by contemporary evaporators for automotive applications.
A first prior art example of a conventional tube and fin heat exchanger is described in Rhodes, U.S. Pat. No. 6,612,031. In this patent, an aluminum tube with multiple partitions within a tube is first extruded, then cut into desired length. These tubes are then combined with additional fins, as tube surface alone is often insufficient and incapable of dissipating heat carried by a heat exchange media. Fins are sandwiched in between each row of tubes comprising a core of a heat exchanger. There are certain drawbacks to this type of heat exchanger cores. First, and foremost, tube extrusions with intricate inner partitions are very difficult to manufacture, requiring precision instruments to obtain a desired shape such as aluminum extrusion machines. An aluminum extrusion machine capable of manufacturing intricate extrusions are often very expensive machines, as well as being notoriously high in operating costs. The more intricate the extrusion shape, an aluminum extrusion machine's extrusion speed has to be reduced not only to obtained a desired shape, but also to protect an extrusion die, as complex extrusion shape causes the extrusion die to be very delicate, prone to damage. Due to the complex nature of extrusion machines, as well as slow operation and delicate extrusion dies that often break during operation, extruded tubes are sold at a relatively high cost, not to mention that there are only a handful of companies with extrusion machines capable of manufacturing intricate tube designs driving up cost of tubes. With tube and fin heat exchanger design, various components are combined together to form a heat exchanger core. These components are typically not designed to maintain its position in relation to each component pursuant to a heat exchanger design parameters during an assembly process, prior to a brazing process which would braze together all components to form a unitary unit. As such, specialized assembly fixtures are often necessary during a manufacturing process to keep the parts together. As a fixture is critical in yielding a good working part, fixtures are often designed to close tolerances resulting in high cost. Also, as a fixture is needed for each heat exchanger assembled at a time, in a large manufacturing operations, where high volume of heat exchangers have to be manufactured at a time, a significant investment has to be made in fixtures, to have on hand enough sufficient quantity of assembly fixtures to support an assembly line. All these investments result in added costs to the manufacturing cost of tube and fin heat exchangers.
Fins utilized are generally of complicated design as described in a second prior art example of a conventional tube and fin heat exchanger in Hiramatsu, U.S. Pat. No. 4,332,293. In this patent, an aluminum tube is combined with corrugated fins to comprise a heat exchanger core. Fins are generally added to tubes to enhance the heat exchange efficiency, as tube surface alone is generally insufficient to handle the necessary heat conduction. Fins discussed in this patent are corrugated to enhance performance of a heat exchanger. Corrugation is added to fins, as flat sheeted fins often do not yield a desired performance expectation. Therefore, fins are generally fabricated with corrugation feature at an additional fabrication cost and manufacturing processes.
A third prior art example of a conventional heat exchanger is commonly known as plate and fin heat exchangers described in Patel, U.S. Pat. No. 3,976,128. In this patent, instead of extruded tubes, individual tubes comprise of two formed plate halves, split along the long axis of the tube. By eliminating usage of extruded aluminum tubes, and by creating individual tubes by combining two formed plates, the main benefit is the cost savings, as formed plates are often less expensive to manufacture in comparison to aluminum extrusion tubes. As with tube and fin heat exchangers, however, tubes of plate and fin heat exchangers often do not have sufficient surface area in relation to the volumetric capacity of a tube assembly to dissipate heat carried by heat exchange media within, rendering a heat exchanger useless without additional surface area addition. In order to enhance performance of plate and fin heat exchangers, fin structures are sandwiched in between each row of formed plate tube structures to obtain added surface area to dissipate heat. There are certain drawbacks to this type of heat exchangers. First, and foremost, although the cost of components may be saved in comparison to extruded tubes, an assembly process of plate and fin heat exchangers remains similar to tube and fin heat exchangers, resulting in a complex assembly process often requiring a specialized assembly fixture to secure all components together until components are brazed together to form a unitary unit in a brazing process. The use of assembly fixture is often vital, driving up initial investment cost necessary to manufacture plate and fin heat exchangers, as significant investment has to be made in assembly fixtures for manufacture of specific configuration heat exchanger cores. Additionally, unlike extruded aluminum tubes, a plate and fin heat exchanger can not be created with too much intricate details, as an assembly of two plate halves are often imprecise, and if a plate design is too intricate, the possibility of misaligning the two halves increase dramatically, rendering a completed heat exchanger useless. Therefore, plate and fin heat exchangers are commonly designed with larger inner partitions, typically resulting in lower performance than extruded aluminum tubes. Another common disadvantage with plate and fin heat exchangers is due to the nature of the design of stacking together plurality of plates without much opening between individual plates. With reduced opening between individual plates, a heat exchange efficiency from a heat exchanger surface to an atmosphere surrounding a heat exchanger media such as air, is often poor, leading to a low efficiency heat exchanger performance.